Wierd video card results after installing Windows 7 Ultimate 64bit?

Before I installed Windows 7 Ultimate I was running XP(SP3) and when I brought up my dxdiag information It listed my Direct X as being 10, and on the display tab it listed my card as a Geforce 9400GT 1G. I just now reinstalled my computer with Windows 7 Ultimate 64bit edition and I also added 2 gigs of RAM. And now when I do dxdiag, it has my Direct X listed as 11, and on my display page the memory of my 9400GT is now 2.2 Gigs. Can anyone explain what the heck happened? is this typo or something? My WEI is online a 4.3 with my processor being the lowest rating and my video card as being a 5.8. Im new to 7 so if anyone can explain what caused my DirectX to upgrade to 11 when im pretty sure 9400GTs aren't 11 compatible, and why my vid card now has 2.2gigs of ddr instead of its original 1 would be awesome. Thank You